Role of mucus layers in gut infection and inflammation.

Abstract

The intestinal mucus is an efficient system for protecting the epithelium from bacteria by promoting their clearance and separating them from the epithelial cells, thereby inhibiting inflammation and infection. The function of the colon inner mucus layer is especially important as this explains how we can harbor the large number of bacteria in our gut. The major component of this mucus system is the MUC2 mucin which organizes the mucus by its enormously large net-like polymers. Pathogenic microorganisms, in turn, have developed mechanisms for circumventing this well-organized mucus protective system.

Schematic outline of the MUC2 mucin and its formation of mucus in the small and large intestine. A. Assembly of the MUC2 mucin (protein core red) into dimeric forms in the endoplasmic reticulum (ER), O-glycosylation (green) in the Golgi apparatus, formation of trimeric forms in the trans Golgi network (TGN) and a schematic picture of the secreted MUC2 polymer. B. The MUC2 mucin is secreted from the goblet cells (black arrows) to form the mucus. Colon have a two layered mucus where the inner layer is converted (red arrows) to the outer mucus layer. The stomach has a mucus essentially as that of colon (not shown). Red dots symbolizes bacteria.